1. Field of the Invention
This invention relates to a carriage for a hard disc device (HDD) used in an information processing apparatus, such as a personal computer.
2. Description of the Related Art
A hard disc device (hereinafter referred to simply as the disc device) is used in an information processing apparatus, such as a personal computer. The disc device comprises magnetic disc for use as a recording medium, a carriage provided with a suspension, a positioning motor for driving the carriage, a box-shaped base, etc. The base contains therein the disc, carriage, positioning motor, etc.
A magnetic head for access to information for the magnetic disc is provided on the distal end portion of the suspension. The “access” described herein implies writing or reading data to or from the disc. The carriage of the disc device is rotated by the positioning motor. Information is read or written by means of the magnetic head that is situated in a target position on the disc.
For example, a 2.5-inch disc device has two discs for use as recording media. The carriage comprises an arm member including a top arm, a bottom arm, and a mid arm provided between the top and bottom arms. One suspension is attached to each of the top and bottom arms. A pair of suspensions are attached to the mid arm so that they are oriented oppositely from each other. A slider that constitutes a magnetic head is mounted on the distal end portion of each suspension. One such suspension is described in Jpn. Pat. Appln. KOKAI Publication No. 2003-173643 or No. 2004-95076.
The top, bottom, and mid arms of the arm member have their appropriate modes (resonance frequencies). The arms swing when a shock is applied to the carriage. In order to improve the resistance of the disc device against the shock during the operation of read or write (hereinafter referred to simply as the operational shock resistance), it is desirable to minimize the swings of the arms when the shock is applied.
As a small, high-integration disc device, such as a 2.5-inch hard disc device, is made thinner and lighter in weight, it becomes more difficult to enhance the modes (resonance frequencies) of the base and the arms. In the disc device of this type, it is essential to effectively suppress the swings of the arms with respect to a short-duration shock that is applied in a short period of time (e.g., 0.4 msec or thereabouts), in particular. Since the arm modes can be enhanced only limitedly, however, some means has been required to improve the operational shock resistance.